Trying that many combinations on one service will raise red flags galore.
Edit: I guess you actually said something more along the lines of "they wouldn't be able to use them all anyway", so my comment doesn't apply as much as I thought it might. The CC company would likely disable the account after enough failed transactions. Still, even a mere fraction of authorizations being successful is pretty significant considering the number of subscribers who have card information stored on the servers. Once they have a working set of cards, they could probably go on a spree with those ones, causing no small amount of trouble for the rightful owners (or the card company, or both). /edit
Why wouldn't they just bounce their IP off a few proxies (or even TOR) or use a bot-net to try the cards for them? If they have the experience to hack the PSN servers and grab account info, they're probably not stupid enough to get caught with a sparkly golden trail leading back to them if or when they use the cards. Identify theft is a very real phenomenon, that doesn't seem to have gotten significantly harder with the advancement of technology. A lot of it's probably good old social engineering, but surely technical expertise facilitates things greatly.
I'm just speculating and making stuff up, though, I don't really know what's possible, plausible, or just plain silly. Sorry if I'm making it sound like "the end is nigh, the end is nigh!", or whatever.
Heck, who knows: maybe it's just an MS fanboy who wants to stick it to Sony. Or, -gasp-, a
Nintendo* fan!
*
"I'm hardcore, I'm hardcore. 13 years old and hardcore. Look at me with my 'moustachio' and red suspenders! ~pika" /no offense intended, it was just an amazingly random thought that came to my head. I actually like Nintendo and the 360 well enough.
